It is well known that dairy products and process streams are a complex mixture of proteins, lipids, sugars and minerals. At present, there are limited methods available for extracting and refining specific components from such streams, and the separation of lipids from proteins in whey-based streams is difficult.
Acid precipitation, heat precipitation, enzymic precipitation, centrifugal separation, membrane filtration and ion exchange are well known methods of separating out components from milk and milk by products. However, these methods are often not cost efficient and often do not produce the desired yields. Also, certain extraction processes must be done under conditions that irreversibly alter the physical properties of the separated components (for example the denaturation of proteins).
WO 91/14377 and WO 92/08363 describe the use of supercritical carbon dioxide and subcritical carbon dioxide for the partial extraction of lipids and fractional precipitation of proteins from dairy products and process streams respectively. However, lipid yields are low using these techniques, with both publications showing limited success and no extraction of useful phospholipids and sphingolipids.
It is therefore an object of the present invention to provide an improved or alternative process for extracting a range of lipids from dairy products and dairy process streams.